Abstract
Aortic corrected flow time (FTc) is easily measured by Doppler techniques. Recent data using transoesophageal Doppler suggest that it may predict fluid responsiveness in critical care. This use of FTc has not previously been evaluated in septic shock, nor have any studies incorporated transcutaneously measured FTc. Furthermore, no comparison has been made between FTc, plasma B-type natriuretic peptide concentration (BNP) or central venous pressure. The aim of this preliminary study was to compare FTc, BNP and central venous pressure as predictors of fluid responsiveness in septic shock patients without cardiac dysrhythmia.
This was a prospective study of 10 consecutive adult septic shock patients (in sinus rhythm; 60% mechanically ventilated) treated with intravenous fluid challenge (4% albumin 250 ml over 15 minutes) in a mixed medical/surgical tertiary intensive care unit.
Mean ± SD Acute Physiological and Chronic Health Evaluation II score was 21.8±12.7. Haemodynamic assessment incorporating transcutaneous aortic Doppler (USCOM®) occurred before and five minutes after fluid challenge. Concurrent with initial assessment, blood samples were collected for BNP assay (ADIVA Centaur®). Four patients demonstrated an increase in stroke volume ≥15% (responders). Percent change in stroke volume strongly correlated with baseline FTc (r=-0.81, P=0.004) but not BNP (r=-0.3, P=0.4) or central venous pressure (r=-0.4, P=0.2). Baseline FTc <350 ms discriminated responders from non-responders (P=0.047).
Our data support FTc as a better predictor of fluid responsiveness than either BNP or central venous pressure in septic shock. Transcutaneous aortic Doppler FTc offers promise as a simple, completely non-invasive predictor of fluid responsiveness and should be evaluated further.